Moving film, direct contact, liquid to liquid heat transfer process

ABSTRACT

A heat transfer process focused for heating or cooling an aggressive liquid employing direct contact through an immiscible fluid film of differing density. The fluid film adheres to a solid wall heat transfer surface purveying both transference of heat therein as well as isolation protection of the heat transfer surface from damage, coating or scaling from the adjacent aggressive liquid.

BACKGROUND

This invention relates to a heat transfer process for heating or cooling an aggresive fluid by means of direct contact with an intermediary, immiscible liquid flowing in a heat conducting mode along the surface of a heat bearing element, said liquid affording both heat transfer from the element to the fluid and protection of the element from the fluid.

Heat transfer processes have purveyed essential benefits to human activity since prehistory, from the natural use of sunlight for body warmth, to the use of fire for cooking and habitat comfort as well the use of water and ice for cooling and preserving food. In modern society, heat transfer processes are exploited in all realms of human activity, such as, cooking, space heating and cooling, fabrication, warfare, transportation, generation of light, preservation of food, medicinal care, chemical conversion processes, to name just but a few.

Essentially, all heat transfer processes employ one or more of three possible methods: conductive, convective and radiative. Conductive heat transfer is a process wherein heat energy is transferred between two or more contacting elements. Conduction is the molecular vibratory energy equalization between contacting elements. An unevenly heated solid element will transfer vibratory heat energy internally until all the matter of the element is at an equal molecular vibratory level. As a result, the colder sections of the element warm and the warmer sections of the element cool. This equalization is internal conduction of heat within the element. Effecting contact between two elements at different temperatures affords conduction between the elements; warming the cooler element and cooling the warmer element. The rate of conduction between the elements is governed by the geometry of both the elements, type of contacting surface, temperature gradients internal to the elements and the physical thermal conductivity properties of the elements.

The convective means of heat transfer employs the physical transport of heated matter from a warmer region to a cooler region or, for the case of convective cooling, the physical transport of chilled matter from a cooler region to a warmer region. Typically this convecting matter is a gas, liquid or plasma (all of which are collectively referred hereafter as a “fluid”). Convective heat transfer incorporates three steps. The first employs heating (or cooling) of the convecting fluid by a thermal source. The second entails physical transport of the heated (cooled) fluid away from the thermal source. The third step ensues when heat is transferred from the warmed (cooled) transported fluid into a cool (warm) separate element by means of direct contact thereof.

Radiative heat transfer differs substantially from conductive and convective heat transfer. This method of heat transfer follows as electromagnetic energy emitted from a thermal source is absorbed by a thermal sink. This radiant energy induces molecular vibration in the absorbing matter, thereby purveying warmth. Radiative heat transfer is the only heat transfer method in which heat can be transferred from a thermal source to a thermal sink across open space. In general, radiative heat processes are employed for heating purposes and rarely for cooling other than those cases wherein an element radiates to ambient surroundings so as to affect energy loss and cooling of the element.

All three of the aforementioned means of heat transfer are employed in industry, with conductive and convective being predominant. Generally, a combination of conductive and convective heat transfer processes are employed by industry. In a typical application, heat is transferred from a thermal source, through the walls of a tube or duct and into a liquid or gas contained therein. The transference of heat from the thermal source to the exterior surface of the tube or duct is primarily by convection. The transference of heat through the metal material of the tube or duct is by conduction and the heat transfered from the interior tubing surface into the liquid or gas is primarily by convection. A typical industrial application of such combined processes would be for thermal change of the chemical, thermodynamic or phase conditions of a liquid, such as the common heating of liquid water to make steam. Another typical example is the employ of the tubing or duct to transport the heated liquid or gas as a heat transfer medium. In such an application, the heated liquid or gas would be transported by means of the tubing or duct to a remote location where the entrained heat is either discharged or employed for process use or space heating.

Conductive processes wherein heat is transferred across a solid wall are common. In such processes, the solid wall generally affords both heat conduction and mechanical separation of the fluids or gases on opposing surfaces of the wall. Heat conduction rate through the solid wall is influenced by the thermal conductivity of the wall material, the temperature differential across the wall, and the wall thickness. High thermal conductivity, high temperature differential, and wall thinness hasten heat transfer while low conductivity, low temperature differential, and wall thickness impede heat transfer.

At a specified temperature differential, conductive heat transfer rates through layered walls are governed by the relative thickness and thermal conductivity of the materials comprising the layers. Heat is transferred through the layers in series. Consequently, the heat transfer rate is hampered by the thickest or least conductive layers. Heat transfer rates are critically impeded by layers of low conductivity materials.

Industry employs countless liquids which experience chemical or physical alterations when heated or cooled. Frequently, these alterations result in the formation or precipitation of solids which deposit and accumulate on surfaces contacting the liquid. Surfaces transferring heat into or out of such liquids are rapidly coated with layers of this accumulating material which nearly always is of very low thermal conductivity. Accordingly, heat transfer rates become useless and the process must be discontinued to facilitate cleaning and removal of the residue accumulations from the heat transfer surfaces. This common and critical problem challenging the heat transfer industry is generally termed “scaling” or “fouling” of the heat exchangers.

Scaling and fouling impede heat conduction rates pursuant to deposition of low thermally conductive (thermally resistant) layers on heat transfer surfaces. As discussed earlier, the heat transfer walls also purvey mechanical separation for materials on opposing sides of the heat transfer surface walls. Aggressive liquids being heated or cooled instigate corrosion and chemical attack upon the heat transfer walls imperiling the mechanical integrity of the heat transfer walls, consequently compromising the requisite fluid separation, thereby adversely compromising both safety and quality concerns related to fluid separation as well reducing the operating life of the heat exchange equipment. Corrosion and chemical attack usually arise from incompatibility of the fluid being heated or cooled and the fabrication material of the heat transfer surfaces. Also, chemical attack is often provoked by chemicals and additives prescribed to reduce or remove scaling and fouling. In such cases, industry generally accepts marginal heat transfer performance or exploits expensive and exotic alloys insensitive to chemical degradation.

Heat exchanger scaling and fouling is a rampant burden on industry. The maintenance, expense and downtime required for cleaning and descaling heat exchangers purveys a daunting encumbrance to industry. Multiple procedures, chemical additives and treatments have been attempted, with limited success to resolve fouling and scaling of heat exchangers

Expensive and maintenance-intensive mechanical methods for continuous or periodic scraping of heat exchanger walls has been employed. These processes, typically referenced as scraped wall heat exchangers, are usually employed wherein the scaling and fouling materials are of value such that the scraping is employed to harvest these materials for marketing. For example, one such approach is described in U.S. Pat. No. 4,616,698, wherein an additional benefit was provided via convection enhancing turbulence. This approach employs a fluidized granular mixture suspended in the fluid being heated.

Abrasion of the circulating grains scour scaling and fouling from the heat transfer surfaces.

Another prevalent method to control scaling on heat transfer surfaces, especially common when heat transfer drives vaporization or evaporation processes, is periodic or continual discharge (blowdown) of the fluid being heated, wherein this blowdown is accompanied by equal volumes of fresh fluid makeup. This technique provides control of the levels of scaling and fouling materials in the fluid, the objective being to maintain scaling and fouling material concentrations below critical levels to reduce the propensity toward scaling and fouling.

Immiscible, liquid to liquid, direct contact heat transfer has been proposed and has been incorporated into limited applications The advantages of the process is the lack of solid heat transfer walls for deposition and agglomeration of scaling and fouling materials. The focus of the majority of the prior art was for transference of heat from fouling, hot brines into immiscible fluids, such as hydrocarbons, which show little solubility with the brines.

The reader is referred to U.S. Pat. No. 4,167,099 as an example of such an approach. This example of the prior art describes employing a multitude of direct contact heat exchange stages to contact an immiscible working fluid, such as a hydrocarbon, with hot geothermal brines. U.S. Pat. No. 3,988,895 decribes a power generation process employing an immiscible working fluid such as isobutene brought into direct heating contact with a hot brine solution. U.S. Pat. No. 4,089,175 disclosed a similar process wherein the direct contact heating process from a highly scaling and fouling brine occurs at or above the critical pressure of a pentane working fluid. Other somewhat similar examples of the prior art are presented in U.S. Pat. No. 1,905,185 as well as U.S. Pat. No. 3,164,957. The direct contact heat exchangers of prior art, as discussed in the foregoing, employ contacting vessels containing solid, essentially immobile sieves, trays or packing. The present inventor also offered an immiscible, direct contact heat exchange process in U.S. Pat. No. 6,119,458 (the “Harris Patent”) wherein a hydrocarbon-based heated fluid flows buoyantly upward, in direct contact, countercurrent flow to a highly scaling brine, while passing through a buoyant, floating bed of oliphilic spheres.

In a common application of the prior art, other than the Harris Patent, isobutane is employed as a working fluid. Isobutane floats upward through the hot brine, being heated in the process and changing phase to a vapor. The isobutene vapor exits the hot brine and is employed for power production or process heating.

Another commercially exploited direct contact heat transfer process used for heat transfer to scaling, fouling liquids employs bubbling of hot gases through a vessel of the scaling, fouling liquid. The hot gases rise through the liquid transferring heat in a direct contact mode. These occasionally used processes are referenced as submerged flame heaters. A similar process wherein superheated steam is employed as the hot contacting gas has also occasionally been employed in industry.

Industry has occasionally employed a radiative heating based process for the heating of scaling, fouling or corrosive liquids. This technique is successful, albeit generally energy inefficient, and has been used for the heating of liquids amenable to electromagnetic radiation absorption. A familiar example of such an art is microwave ovens for heating water entrained foods and drinks.

Heat transfer processes of the prior art involving scaling, fouling or corrosive liquids confer expensive, detrimental and profound challenges. Many problems, limitations and disadvantages burden the prior art when heat transfer involves scaling, fouling or corrosive liquids:

Corrosion problems are often addressed by the employ of more chemically compatible fabrication materials which are often either expensive, difficult to machine or work, uncommon and/or burdened by poor thermal conductivity.

Chemical treatment of corrosive liquids affords some benefits, however chemistry and contamination problems, as well as high expense, commonly encumber any benefits proffered by these efforts of the prior art.

Reduction of scaling and fouling tendencies by means of chemical addition is usually costly as well as unreliable in many applications wherein liquid chemistry normally varies. Further, many of the common treatment chemicals are quite hazardous, burdening operations with safety and environmental liabilities.

Scaling and fouling inhibition by chemical treatment only affords limited protection. Chemical treatment generally only conveys reduction of the required frequency of heat transfer surface cleaning maintenance. Expensive, troublesome and potentially hazardous cleaning maintenance is still required for maintenance of heat transfer efficiency, albeit less often.

Heat transfer surfaces are corroded or damaged by many of the harsh cleaning and treatment chemicals employed to control scaling and fouling. In response, heat transfer surfaces in industry are often fabricated of exotic, expensive, and rare materials. In addition to expense, fabrication difficulties and availability burden the employ of such materials. Further, reduced thermal conductivity often compromises the thermal performance of equipment manufactured of these materials; requiring higher temperature differentials or larger heat transfer surfaces. Higher temperature differentials encumber energy use whereas larger heat transfer surface area exaggerates both heat transfer equipment cost and spatial demands.

Those heat transfer processes employing blowdown and makeup frequently also use treatment chemicals to minimize the blowdown and makeup volumes. Consequently, blowdown is entrained with residual chemical and associated by-products. These materials are often hazardous, occasioning difficulties, expenses and liabilities related with handling, treating and disposal.

Control of scaling and fouling by means of blowdown and makeup require monitoring of liquid properties for maintenance of appropriate discharge and recharge rates. Excursions from such control results in excess expense and discharge liabilities if the rates are excessive and fouling, scaling and potential damage if the rates are inadequate.

Mechanical complexities and associated expense and maintenance burden scraped wall heat exchangers. Similarly, granular abrading heat exchangers are burdened by pumping mechanics and piping constraints prone to plugging and failure.

The scraping and abrasion action accompanying scraped wall heat exchangers requires the composition of the heat transfer surfaces to be hard and often thick. Additionally, chemical resistance is commonly required of the wall material. Consequently, the required wall materials are exotic, expensive and difficult to manufacture. Further these materials often compromise thermal conductivity for other factors. The thicker and lower conductivity walls substantially burden scraped wall heat exchangers with poor heat transfer performance. Accordingly, higher temperatures or larger heat transfer surface areas are required. Higher temperatures imbue higher energy use and larger heat transfer surface area demands both higher heat transfer equipment cost and spatial demands.

Direct contact, immiscible liquid-to-liquid heat exchange processes of the prior art suffer from impaired efficiencies due to attraction and agglomeration of the contacting liquids. Agglomeration of immiscible fluid droplets, as they pass through the entraining liquid inflates the droplet size and reduces the population of droplets. Both these effects reduce the surface area of the immiscible fluid contacting the entraining fluid, reducing the heat transfer rate between the fluid and entraining liquid.

Submerged flame processes of the prior art are expensive, difficult to maintain and are substantial consumers of high quality energy. This the submerged flame processes of the prior art also require troublesome and expensive air pollution emission control equipment. Maintenance efforts incited by plugging and fouling are difficult and the benefits are often short lived. Ineffective maintenance of the pollution control equipment incites substantial safety and environmental liabilities conveying significant disadvantage to the prior art of submerged flame heat exchange.

Submerged combustion processes of the prior art are burdened by the generation of reverse solubility precipitates during the heat transfer process. Rising gas bubbles produce turbulence which prevents settling of precitates engendering an accumulation of suspended solids within the liquid volume. These materials cause plugging and fouling of the vessels, pipes and pumps associated with the submerged flame device.

Direct heating by steam injection is quite limited to only those applications in which contamination of the heated fluid by steam condensate is acceptable.

Radiative heating has seen limited use due to high operational cost, inefficiency and capital expense. This example of the prior art requires radiative absorption of the liquid being heated. Often this liquid is transparent and radiative absorption by the liquid is not possible.

The usual source of radiation employed is a high temperature thermal source such as generated by electric resistance heating, fuel combustion or electromagnetic generation. These sources all generate non-radiative heat which is conducted or conveyed from the process and wasted, resulting in low efficiency. An additional inefficiency afflicts radiative heating resulting from a typical liquid characteristic wherein radiative energy is only absorbed over a limited wavelength range. Radiation outside of this range is wasted.

Microwave heating, as a form of radiative heat transfer into aqueous based liquids, is common in many households and dining establishments. This process works rapidly although inefficiently with only aqueous based liquids.

SUMMARY

The present invention generally relate to a heat transfer process, which is generally referred herein as “heating” but, as would be obvious to one skilled in the art, the process described herein is equally applicable to cooling an aggressive liquid (the liquid) without scaling or corrosive damage to heat transfer surfaces. The heat transfer process described herein employs heat transfer to the liquid by means of direct physical contact between the liquid and a fluid with a different density and immiscibility with no solubility for scaling solutes (the fluid), provisioned as a protective film upon a heated heat transfer surface. The heated surface transfers heat into the protective fluid film, which in turn, by direct contact, transfers heat to the liquid.

In one embodiment, a heat transfer device employing the process may include a vessel with at least two liquid conveyances of which at least one purveys ingress of a cold liquid aggressive to the interior of the vessel and another purveys egress of warmed liquid from the vessel. In this aspect, the vessel may be afforded with at least one fluid conveyance to egress cold immiscible fluid from the vessel. In this aspect, there is at least one hollow tube vertically suspended into the liquid within the vessel, the lower end of the hollow tube being open, the upper open end of the hollow tube being elevated above the liquid. The hollow tube may be suspended from, and open into, an overhead vessel, the overhead vessel including at least one conveyance port for ingress of heated immiscible fluid of differing density than the aggressive liquid. The fluid and the liquid may have relative surface tension characteristics purveying preferential wetting of the material of the hollow tube by the fluid rather than the liquid. In this aspect, the fluid is of lower density than the liquid.

In another embodiment, a process of heating liquids includes the steps of:

conveying reduced temperature liquid via an ingress conveyance into a vessel; conveying increased temperature fluid via an inlet conveyance into the overhead vessel, fluid flowing down the hollow tube from the overhead vessel, heating the hollow tube as the heated fluid conveys downward therein, exiting the lower open end of the hollow tube into direct contact with the liquid, fluid buoying upward in the denser liquid while in full wetting adherence to the tube external wall, rising adherence of the fluid purveying a protective sheath like film completely about the submerged tube surface, heat transferring from the internally conveyed heated fluid into the walls of the hollow tube, heat transferring from the walls of the hollow tube into the rising fluid film sheath, heat transferring from the rising fluid film sheath into the surrounding liquid; rising fluid films sheath separating from the hollow tube above the liquid, cooled fluid collecting on top of the liquid, cooled fluid egressing the vessel for external reheating; heated liquid egressing the vessel for external use having never physically contacted and endangered the surface of the tube.

The foregoing and other aspects and implementations of a rising film heat exchange process and device may have one or more or all of the following advantages, as well as other benefits discussed elsewhere in this document. Heat transfer with aggressive liquids can be efficiently afforded without the impediments associated with scaling, fouling or corrosion of heat transfer surfaces.

Corrosion resistant materials are not required, eliminating the associated detriments of expense, fabricating complexities and poor thermal performance.

Corrosion inhibitors and other chemical treatments common with corrosive liquids are not required, thereby eliminating potential contamination problems and chemical treatment expenses.

Chemical scale inhibitors and solids dispersants are not required eliminating the associated expense.

Heat transfer reliability is enhanced in applications with varying liquid quality and constituents.

Personnel and environmental hazards associated with chemical scale inhibitors and solid dispersants are eliminated.

Heat transfer surface cleaning maintenance is eradicated, eliminating the associated expense, downtime and hazardous chemical usage.

Aggressive heat transfer surface cleaning agents and associated cleaning operations are not employed, eliminating the requirements for exotic or thermally compromising materials necessary to withstand the detrimental effects of cleaning chemicals and associated operations.

Chemical scale and corrosion inhibitors and dispersants are not employed thereby affording the safety, convenience, and assurance of chemical free blowdown, if needed.

The heat transfer surfaces require no exotic hard or thick materials or mechanical or hydraulic complexities associated with scraped wall or abrading solids entrained liquid heat transfer processes.

Maintenance and control of direct contact, immiscible liquid heat transfer geometry is afforded by the constant moving immiscible film sheath about the heat transfer tube surface, eliminating loss of heat transfer surface due to either free immiscible fluid agglomeration or channeling phenomenon.

Energy transfer is efficient and environmentally clean affording no maintenance, plugging, fouling or air pollution potential in contrast to such hindrances associated with submerged flame heat transfer processes.

Heating vapor condensation contaminates, such as burdens steam injection heat transfer processes, are not possible.

Heat transfer is efficient and direct without the energy loss associated with radiative or microwave heat transfer processes.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of one embodiment the subject process wherein a lower density immiscible heat transfer fluid with no solubility for scaling solutes is employed to transfer heat with a higher density aggressive liquid;

FIG. 2 is a schematic diagram of one embodiment the subject process wherein a higher density immiscible heat transfer fluid with no solubility for scaling solutes, is employed to transfer heat with a lower density aggressive liquid;

FIG. 3 is a schematic diagram of a device wherein a lower density immiscible fluid, with no solubility for scaling solutes, is employed to transfer heat with a higher density aggressive liquid; and

FIG. 4 is a schematic diagram of a device wherein a lower density immiscible fluid, with no solubility for scaling solutes, is employed to transfer heat with a higher density aggressive liquid.

DETAILED DESCRIPTION OF THE DRAWINGS

The making and use of the process and example embodiments of the device are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention. The present invention will be described with respect to various embodiments in a specific context, namely as a device and process for heating an aggressive liquid by submersion of a heated surface in the aggressive liquid wherein the heated surface is protected from the aggressive liquid by a film of a separate and immiscible fluid coating the heated surface. In some embodiments, process and device employ a protective, immiscible fluid of lower density than the aggressive liquid thereby impelling buoyant rising carriage and separation of the immiscible fluid from the aggressive liquid. The invention may also be applied wherein the immiscible fluid is denser than the aggressive liquid thereby impelling a sinking carriage and separation of the immiscible fluid from the aggressive liquid. The process may be further enhanced through the employ of an immiscible fluid having low solubility for scale forming solutes. In addition, the immiscible fluid and aggressive liquid may present relative surface tension characteristics affording preferential adherence of the fluid to the heat transfer surfaces.

As should be obvious to those skilled in the art that the processes and device implementations described herein may also be readily applied to applications wherein cooling or cyclical heating or cooling functions of the aggressive liquid are sought. Wherein with cooling applications the simple shift to cooler immiscible fluid addressing a warmer aggressive liquid obviously pertains. The processes and devices of the subject invention may also be readily applied in multiple and diverse other applications wherein the invention addresses heating or cooling of many types of liquids, not being limited to aggressive liquids.

There are many features of the heat transfer process and device implementations disclosed herein, of which one, a plurality, or all features or steps may be employed in any particular implementation.

In the following description, reference is made to the accompanying-figures which form a part hereof, and which show by way of illustration possible implementations. It should be understood that other implementations may be utilized, and structural, as well as procedural, changes may be made without departing from the scope of this disclosure. As a matter of convenience, various components will be described using exemplary materials, sizes, shapes, dimensions, and the like. However, the invention is not limited to the stated implementations and examples and other configurations are possible and within the teachings of the present disclosure.

A heat transfer process and device is described herein with respect to implementations in specific contexts. Furthermore, it should be appreciated by those skilled in the art that the conception and specific implementations disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present disclosure. It should be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of this disclosure.

Various embodiments of the invention employ an immiscible fluid with low solubility for scale forming solutes to both transfer heat into an element submerged in an aggressive liquid and to coat and protect the element from being damaged or impaired by the aggressive liquid. Further, the immiscible fluid is motivated for travel within and collection without the aggressive liquid because of the differing density between the immiscible fluid and the aggressive liquid. Additionally, in one embodiment, the immiscible fluid provides coated protection of the heated element as a consequence of preferential wetting of the element by the immiscible fluid in deference to the aggressive liquid.

In a general process description of one embodiment, a warmer, lower density, immiscible fluid with no solubility for scale forming solutes is conveyed into the upper end of a heat exchanger tube, which is vertically submerged within but extending upwards without an aggressive liquid. The liquid is of a higher density than the immiscible fluid. The aggressive liquid would normally damage or impair the materials or heat transfer capability of the heat transfer tube.

The heated immiscible fluid transfers heat into the heat exchanger tube wall material as the fluid conveys vertically downward within the tube, thereby cooling the immiscible fluid concurrent with heating the tube.

The lower end of the tube is open to the surrounding cooler and higher density aggressive liquid. The cooled immiscible fluid exits the lower open end of the tube into direct contact with the surrounding aggressive liquid. The lower density of the immiscible fluid relative to the aggressive liquid buoys the immiscible fluid upward as it exits the lower end of the heat exchanger tube.

Preferential wetting of the heat exchanger tube by the immiscible fluid purveys adherence of the rising immiscible fluid as a film-like sheath about the outside surface of the heat exchanger tube, thereby physically separating the aggressive liquid from the heat exchanger tube and protecting the tube accordingly.

As the immiscible fluid sheath rises along the heat exchanger tube external wall, heat sourced from the heated downward flowing immiscible liquid within the tube transfers into the tube wall. The heated tube wall in turn heats the external immiscible fluid rising in the film-like sheath about the tube. The heated immiscible fluid comprising the rising sheath, in turn, heats the surrounding aggressive liquid by direct contact thereof.

The immiscible fluid sheath rises to the top surface of the aggressive liquid where it separates from adherence with the tube forming a layer of immiscible fluid on the surface of the aggressive liquid. The warmed aggressive liquid egresses the process for external use from below the immiscible fluid layer. The cool immiscible fluid egresses the process from above the aggressive liquid for reheat and continuation of the heat exchange process.

With reference now to FIG. 1, one embodiment of the present invention employs a vertically oriented, thermally conductive tube 100 with one end 102 submerged within an aggressive liquid 104 and the other end 106 extending without the aggressive liquid 104.

A fluid 108 ingresses the upper tubing end 106. Fluid 108 is hotter than, immiscible with, and of lower density than liquid 104. Further, fluid 108, in deference to liquid 104, preferentially wets the surface material of tube 100.

Fluid 108 conveys downward in tube 100 heating the tubing walls of tube 100 as fluid 108 conveys downward therein. Fluid 108 egresses the lower opening 102 of tubing tube 100, entering into the environs of liquid 104. The higher density of liquid 104 buoys fluid 108 upward upon egressing the tube end 102.

The preferential wetting of the external wall of the tube 100 by the fluid 108 rather than the surrounding liquid 104 incites adherence of fluid 108 to the external wall of tube 100 as fluid 108 buoys upward by the higher density of surrounding liquid 104. The adherence of the rising fluid 108 to the external wall of the tube 100 forms a rising sheath 110 about tube 100. Sheath 110 protects tube 100 from detrimental contact with liquid 104. The tubing 100 is heated by internal conveyance of the heated fluid 108. The heated wall of tube 100 heats the rising sheath 110 which in turn, by direct contact, heats the surrounding liquid 104

Upon rising to the upper surface of liquid 104, fluid sheath 110 degenerates and fluid 108 disperses as an immiscible floating layer 112 above the liquid 104.

FIG. 2 depicts a similar, albeit mirrored, process to FIG. 1. One embodiment of the present invention employs a vertically oriented, thermally conductive tube 101 with one end 103 rising into an aggressive liquid 105 and the other end 107 extending through a sealing wall 115 to an isolated region below liquid 105 and sealing wall 115.

A fluid 109 ingresses the lower tubing end 107. Fluid 109 is hotter than, immiscible with, and of higher density than liquid 105. Further, fluid 109, in deference to liquid 105, preferentially wets the surface material of tube 101.

Fluid 109 conveys upward in tube 101 heating the tubing walls of tube 101 as fluid 109 conveys upward therein. Fluid 109 egresses the upper opening 103 of tubing tube 101, entering into the environs of liquid 105. The higher density of fluid 109 in the environs of liquid 105 incites a sinking motion of fluid 109 upon egressing the tube end 103.

The preferential wetting of the external wall of the tube 101 by the fluid 109 rather than the surrounding liquid 105 incites adherence of fluid 109 to the external wall of tube 101 as fluid 109 sinks downward in the lower density of the surrounding liquid 105.

The adherence of the sinking fluid 109 to the external wall of the tube 101 forms a falling sheath 111 about tube 101. Sheath 111 protects tube 101 from detrimental contact with liquid 105. The tubing 101 is heated by internal conveyance of the heated fluid 109. The heated tube 101 heats the falling sheath 111, which in turn, by direct contact, heats the surrounding liquid 105. Upon sinking to the bottom of liquid 105, fluid sheath 111 degenerates and fluid 109 disperses as an immiscible layer 113 below the liquid 105.

FIG. 3 depicts a similar situation to FIG. 1, albeit inclusive of a physical vessel with conveyance features and associated ingress and egress flows. This embodiment of the present invention so illustrated employs an essentially vertical vessel 214 with an ingress 218 and two egress conveyance ports 216 and 220 wherein 216 is located at a higher elevation in vessel 214 than 220. A vertically oriented, thermally conductive tube 200 has one end 202 submerged within an aggressive liquid 204 and the other end 206 extending without the aggressive liquid 204. Aggressive liquid 204 has ingress to vessel 214 by means of conveyance port 218.

A fluid 208 ingresses the upper tubing end 206. Fluid 208 is hotter than, immiscible with, and of lower density than liquid 204. Further, fluid 208, in deference to liquid 204, preferentially wets the surface material of tube 200. Fluid 208 conveys downward in tube 200 heating the tubing walls of tube 200 as fluid 208 conveys downward therein. Fluid 208 egresses the lower opening 202 of tubing tube 200, entering into the environs of liquid 204. The higher density of liquid 204 buoys fluid 208 upward upon egressing the tube end 202.

The preferential wetting of the external wall of the tube 200 by the fluid 208 rather than the surrounding liquid 204 incites adherence of fluid 208 to the external wall of tube 200 as fluid 208 buoys upward by the higher density of surrounding liquid 204.

The adherence of the rising fluid 208 to the external wall of the tube 200 forms a rising sheath 210 about tube 200. Sheath 210 protects tube 200 from detrimental contact with liquid 204.

The tubing 200 is heated by internal conveyance of the heated fluid 208. The heated wall of tube 200 heats the rising sheath 210 which in turn, by direct contact, heats the surrounding liquid 204. Upon rising to the upper surface of liquid 204, fluid sheath 210 degenerates and fluid 208 disperses as an immiscible floating layer 212 above the liquid 204. Conveyance port 220 affords egress of the now warmed liquid 204 from the vessel 214 for external process use. The cooled fluid 208 egresses the layer 212 and the vessel 214 by conveyance port 216.

With reference now to a preferred embodiment illustrated in FIG. 4, in addition to the process embodiment presented by FIG. 3, this embodiment employs a multitude of heat exchanger tubes communicating with an overhead vessel. Further, the aggressive liquid containment vessel employs a method to support fluid levels therein.

This preferred embodiment employs an essentially vertical vessel 314 with an ingress 318 and two egress conveyance ports 316 and 320 wherein 316 is located at a higher elevation in vessel 314 than 320. An aggressive liquid 304 purveys ingress to vessel 314 by means of a conveyance port 318. A plurality of vertically oriented, thermally conductive tubes 300, are positioned having their lower ends 302 submerged within aggressive liquid 304, and the other upper ends 306 extending without the aggressive liquid 304 and into, and in hydraulic communication with, an overhead fluid containment vessel 322.

Ingress to vessel 322 purveys by conveyance 324 and egress from vessel 322 by the open tube ends 306. A fluid 308 ingresses vessel 322 through ingress conveyance port 324. Fluid 308 is hotter than, immiscible with, and of lower density than aggressive liquid 304. Further, fluid 308, in deference to liquid 304, preferentially wets the surface material of tube 300.

Hot fluid 308 egresses vessel 322 by entry into the upper open ends 306 of the tubes 300. Fluid 308 conveys downward in tubes 300, heating the tubing walls of tubes 300 as fluid 308 conveys downward therein. Fluid 308 egresses the lower openings 302 of tubes 300 and enters the environs of liquid 304. The higher density of liquid 304 buoys fluid 308 upward upon egression from the tube ends 302.

The preferential wetting of the external wall of the tubes 300 by the fluid 308 rather than the surrounding liquid 304 incites adherence of fluid 308 to the external walls of tubes 300 as fluid 308 buoys upward by the higher density of surrounding liquid 304. The adherence of the rising fluid 308 to the external wall of the tubes 300 forms a rising sheath 310 about tubes 300. Sheath 310 protects tubes 300 from detrimental contact with liquid 304.

The internal conveyance of the heated fluid 308 heats the walls of the tubes 300. In turn, the heated walls of tubes 300 heat the rising sheaths 310 which, by direct contact, heat the surrounding liquid 304

Upon rising to the upper surface of liquid 304, fluid sheaths 310 degenerate and fluid 308 disperses as an immiscible floating layer 312 above the liquid 304.

Overflow weir 328 affords egress of the now warmed liquid 304 from the vessel 314 into a fluid leveling balance line 332. Fluid leveling balance line 332 and overflow weir 328 provide fluid level control within vessel 314.

In one embodiment, vessel 314 is cylindrical wherein the overflow weir 328 presents an annular collection region around the internal perimeter of vessel 314. Ingress conveyance 318 disperses the cold, aggressive liquid 304 central to and in the lower region of vessel 314. In combination with the annular overflow weir 328, this configuration conveys an upward and radially outward flow of the aggressive liquid 304 in the vessel 314 and about the tubes 300; imbuing both thermal countercurrent up-flow and radial fluid cross flow, provisioning superior thermal transfer performance.

The now warmed liquid 304 egresses, for external process use, from the fluid leveling balance line 332 at egress conveyance 320.

Cooled fluid 308 egresses the floating layer 312 and the vessel 314 by conveyance port 316. After being externally and independently reheated, fluid 308 returns to ingress port 324 for continuation of the process.

The simple and novel features of the process and devices described herein purvey heat transfer with an aggressive liquid through the employ of an immiscible fluid to both carry heat to a heat transfer surface and to protect that surface from damaging effects of the aggressive liquid.

A further novel feature of the subject process and device is the employ of an immiscible fluid of differing density than the aggressive fluid, facilitating natural and simple movement and separation of the immiscible fluid and aggressive liquid.

Another novel feature of the subject art is the preference of the immiscible fluid rather than the aggressive liquid to wet the heat transfer surfaces; thereby purveying tenacious adherence of the immiscible fluid to the heat transfer surfaces, effectively isolating and reliably protecting these surfaces from the aggressive liquid.

Another novel effect is provision of direct contact, reliable and efficient heat transfer within scaling liquids wherein, were it not for the adherence and protection facilitated by the immiscible fluid unto heat transfer surfaces, scaling or fouling of said surfaces would impede heat transfer.

Another novel effect is provision of direct contact, reliable and efficient heat transfer within scaling liquids without the necessity of scale inhibiting chemicals addition.

Another novel effect is provision of direct contact, reliable and efficient heat transfer within scaling liquids without the requirement for mechanical scrapping or abrading to remove heat transfer inhibiting scale or fouling.

Another novel effect is provision of direct contact, reliable and efficient heat transfer within corrosive liquids without the requirement for chemical corrosion inhibitors to protect heat transfer surfaces.

Another novel effect is provision of direct contact, reliable and efficient heat transfer within corrosive liquids without the requirement for exotic or expensive, corrosion resistant, heat transfer materials.

Another novel effect is provision of direct contact, reliable and efficient heat transfer within scaling or corrosive liquids without the requirement for blowdown or dilution to reduce scaling or corrosion effects.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. Finally, in the foregoing discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. 

What is claimed is:
 1. A method for transferring heat between a liquid and a fluid comprising: partially submerging the lower end of at least one tube within a liquid, wherein the upper end of said at least one tube is above said liquid; allowing a fluid to access the upper end of said at least one tube, wherein said fluid is immiscible with said liquid, and wherein said fluid is a different temperature than said liquid, thereby directly transferring heat between said fluid and said liquid; and as said fluid leaves said lower end of said at least one tube and rises, said fluid separates said at least one tube from said liquid.
 2. The method of claim 1, wherein said fluid is heated and, as said fluid passes through said at least one tube, said fluid heats said at least one tube in passing and, as said fluid leaves said lower end of said at least one tube, said fluid maintains contact with said at least one tube, thereby separating said liquid from said at least one tube.
 3. The method of claim 1, wherein said separation afforded by said fluid between said liquid and said at least one tube prevents damage to, or coating of, said at least one tube from said liquid or constituents entrained therein.
 4. The method of claim 1, wherein said at least one tube is preferentially wetted by said fluid in deference to said liquid thereby enhancing adherence of said fluid to said at least one tube and purveying improved heat transfer from said at least one tube through said fluid to said liquid.
 5. The method of claim 1, wherein said at least one tube is preferentially wetted by said fluid in deference to said liquid thereby enhancing adherence of said fluid to said at least one tube and providing improved protection from damage to, or coating of, said at least one tube from said liquid or constituents entrained therein.
 6. The method of claim 1, wherein said fluid is cooled below the temperature of said liquid and said fluid cools said at least one tube when passing through said at least one tube.
 7. A device for transferring heat between a fluid and a liquid comprising: a container containing a liquid; one or more tubes configured so all upper ends of said one or more tubes are above said liquid and all lower ends of said one or more tubes are submerged in said liquid; a fluid positioned to be accessible to said upper ends of said one or more tubes, said fluid being immiscible with said liquid and having a different temperature and density than said liquid; wherein as said fluid accesses said one or more tubes, heat is transferred between said fluid and said liquid; wherein said differing density purveys relative motion between said fluid and said liquid; and wherein, after said fluid passes through said lower ends of said one or more tubes, said fluid affords separation between said one or more tubes and said liquid.
 8. The device of claim 7 wherein said fluid is heated and, as said fluid accesses said upper ends of said one or more tubes and passes through said one or more tubes, said fluid heats said one or more tubes and said one or more tubes heat said liquid.
 9. The device of claim 7 wherein said separation provides protection from damage to, or coating of, said one or more tubes from said liquid or constituents entrained therein.
 10. The device of claim 7 wherein said one or more tubes is preferentially wetted by said fluid in deference to said liquid, thereby enhancing adherence of said fluid to said one or more tubes and improving heat transfer between said one or more tubes and said liquid through said fluid.
 11. The device of claim 7 wherein said one or more tubes is preferentially wetted by said fluid in deference to said liquid thereby enhancing adherence of said fluid to said one or more tubes, thereby improving protection from damage to, or coating of, said one or more tubes from said liquid or constituents entrained therein.
 12. The device of claim 7 wherein said fluid is cooled and, as said fluid accesses the upper end of said one or more tubes and passes through said one or more tubes, said fluid cools said one or more tubes and said one or more tubes cools said liquid.
 13. The device of claim 7 wherein said immiscibility and said differing density affords separation of said fluid and said liquid subsequent to heat transfer.
 14. A heat transfer system comprising: a. a first container containing a liquid, said first container having at least one liquid ingress, at least one liquid egress and at least one fluid egress; b. at least one vertical tube with a first end positioned within said liquid and a second end positioned to receive a fluid from a second container, wherein said fluid is immiscible with said liquid and wherein said fluid and said liquid are of differing density; c. wherein as said fluid passes from said second container through said tube, heat is transferred between said fluid and said liquid; d. wherein said differing density purveys relative motion between said fluid and said liquid; and e. wherein upon exiting said tube, said fluid affords separation between said tube's external surface and said liquid.
 15. The device of claim 14 wherein said fluid is conveyed into said second container, wherein said second container is elevated relative to said first container and wherein said liquid is cooler and denser than said fluid, as said fluid passes from said second container downward through said tube, said fluid heats said tube, thereby cooling said fluid, as said fluid exits said first end of said tube into said liquid, said fluid, due to its lower density than said liquid rises upward while adhering in a film-like sheath to said tube's external surface, said tube thereby transferring heat to said fluid as it rises which, in turn, transfers heat to said liquid, wherein movement of said liquid between said at least one liquid ingress and said at least one liquid egress creates movement of said liquid in said first container and, therefore, across said sheath, thereby imbuing heat transfer from said sheath to said liquid; and wherein, after said fluid rises above said liquid, said fluid exits said first container through said at least one fluid egress.
 16. The device of claim 14 wherein said fluid is conveyed into said second container, wherein said second container is elevated relative to said first container and wherein said liquid is warmer and denser than said fluid, as said fluid passes from said second container downward through said tube, said fluid cools said tube, thereby warming said fluid, as said fluid exits said first end of said tube into said liquid, said fluid, due to its lower density than said liquid rises upward while adhering in a film-like sheath to said tube's external surface, said tube thereby extracting heat from said fluid as it rises which, in turn, extracts heat from said liquid, wherein movement of said liquid between said at least one liquid ingress and said at least one liquid egress creates movement of said liquid in said first container and, therefore, across said sheath, thereby extracting heat from said sheath to said liquid; and wherein, after said fluid rises above said liquid, said fluid exits said first container through said at least one fluid egress.
 17. The device of claim 14 wherein said fluid is conveyed into said second container, wherein said second container is lower relative to said first container and wherein said liquid is cooler and denser than said fluid, as said fluid passes from said second container upward through said tube, said fluid heats said tube, thereby cooling said fluid, as said fluid exits said first end of said tube into said liquid, said fluid, due to its higher density than said liquid moves downward while adhering in a film-like sheath to said tube's external surface, said tube thereby transferring heat to said fluid as it falls which, in turn, transfers heat to said liquid, wherein movement of said liquid between said at least one liquid ingress and said at least one liquid egress creates movement of said liquid in said first container and, therefore, across said sheath, thereby transferring heat from said sheath to said liquid; and wherein, after said fluid falls below said liquid, said fluid exits said first container through said at least one fluid egress. 